The periodontium, the tissues investing and supporting teeth, includes aveolar bone, root cementum, periodontal ligament, and gingiva. It is generally accepted that the etiology of periodontal disease(s) is infectious in origin, however, variations in the host allow a range of disease expression. Invariably the disease process results in irreversible tissue loss resulting in disfiguration and phonetic imparement in its advanced stages. Approaches to therapy of periodontal disease(s) include elimination of the infection. However, this may not restore necessary form and function. These periodontal defects exhibiting crippling loss of alveolar bone, periodontal ligament, and gingiva should be considered for reconstructive therapy or the involved teeth be amputated and replaced by a prosthesis. However, due to the recent advances in genetic engineering, there is another possibility. If one knows the factors involved in regrowth of tissue, those factors could be delivered and regrowth allowed. Animal models offer the opportunity for histologic observations, which may contribute, to enhanced understanding of the biology of healing following reconstructive procedures. In the proposal, the investigators describe a unique mouse model of tissue regeneration with a defined genetic basis. Published observations in the model include the normal replacement of cartilage and skin. They will use an established experimental periodontal defect in this mouse model to 1) determine if regeneration actually occurs and if so, advance the understanding of temporal and spatial events leading to regeneration of the periodontium, 2) determine gene expression at the site of healing and analyze potential molecules to enhance healing, and 3) determine if congenic mice which have already been selected for the genes involved in regeneration of ear tissue also display periodontal healing.